Pop-up irrigation sprinklers, in some cases, are buried in the ground and include a stationary housing and a riser assembly mounted within the housing that cycles up during an irrigation cycle and, then, back down into the housing after irrigation is complete. During irrigation, pressurized water typically causes the riser assembly to elevate through an open upper end of the housing and rise above the ground level to distribute water to surrounding terrain. The pressurized water causes the riser assembly to travel upwards against the bias of a spring to the elevated spraying position to distribute water to surrounding terrain through one or more spray nozzles. When the irrigation cycle is completed, the pressurized water supply is shut off and the riser is spring-retracted back into the stationary housing.
A rotary irrigation sprinkler commonly includes a rotatable nozzle turret mounted at the upper end of the riser assembly. The turret includes one or more spray nozzles for distributing water and is rotated through an adjustable arcuate water distribution pattern. Rotary sprinklers commonly include a water-driven motor or other mechanism to transfer energy of the incoming water into a source of power to rotate the turret. One common mechanism uses a water-driven turbine and a gear reduction system to convert the high speed rotation of the turbine into relatively low speed turret rotation. During normal operation, the turret rotates to distribute water outwardly over surrounding terrain in an arcuate pattern.
Rotary sprinklers may also employ arc adjustment systems to change the relative arcuate distance between two stops that define the arcuate limits of rotation for the turret. One stop is commonly fixed with respect to the turret while the second stop can be selectively moved arcuately relative to the turret to increase or decrease the desired arc of coverage. The drive motor may employ a tripping tab that engages the stops and shifts the direction of rotation of the motor output to oscillate the turret in opposite rotary directions in order to distribute water of the designated arc defined by the stops.
There is generally a relationship between the amount of water discharged from a sprinkler nozzle relative to its arc of oscillation at a given speed of rotation. This is commonly referred to as the precipitation rate for the sprinkler, and it relates to how much irrigation water is projected onto a ground surface area defined within the arc of rotation. As the arc of rotation is increased or decreased, the flow of water through the nozzle should be adjusted accordingly so that the same precipitation rate is deposited on the ground independent of the sprinkler's arc of rotation. This concept is often referred to as a matched precipitation rate. Previously, a matched precipitation rate was achieved by switching nozzle configurations when the arc is changed by manually removing and inserting different nozzle inserts for each arc setting. As can be appreciated, this is a cumbersome task and requires multiple nozzle inserts configured for specific arcs of rotation. For example, a sprinkler may have one nozzle insert for a 45° arc of rotation and a different nozzle insert for a 90° arc of rotation. For non-standard arc settings (such as a 67° arc of rotation for example), there may not an appropriate standard-size nozzle insert to achieve matched precipitation. Thus, in many instances, the non-standard arc settings often rely on a less then desired nozzle insert that may be mismatched to the selected arc of rotation. That is, a 67° arc of rotation may need to rely on a 45° or a 75° nozzle insert, but such nozzle insert may not be tailored to provide a desired precipitation rate for a 67° arc of watering.